Crop farmers collect, transport and disperse various kinds of dry agricultural materials as they plant, nurture and harvest their crops. Combine harvesters, for example, reap, thresh and winnow wheat, oats, rye, barley, corn, soybeans, flax and other crops. Grain collected in a combine is usually transferred first to grain carts and later to trucks for transport to silos or grist mills. Other kinds of dry agricultural materials include gravel, sand, salt, some fertilizers, herbicides and pesticides. Here, “dry” is in contrast to liquids such as water or aqueous solutions. “Dry” material need not be devoid of moisture, but “dry” does imply more friction with container walls than a liquid has, and minimal sloshing behavior.
Modern farms are sophisticated biomaterial factories that run complex production processes. Achieving high crop yield depends on precision management of land, machines, labor and materials. The more parts of a production process that can be measured, the more insight a farmer can obtain on where improvements are possible. Dry agricultural materials like grain are normally dealt with in truck size units, thousands of pounds at a time. Efficient management of these materials depends critically on the ability to measure the quantity of material on a truck or in a storage bin, and the rate of increase or decrease of that quantity; i.e. how fast a bin is filling or emptying.
FIG. 1 shows examples of the collection and dispersal of dry agricultural materials. In “A”, a combine harvester is unloading grain to a cart; in “B” a spreader truck is spreading material over a field. Farmers need to know the answers to questions such as: How much grain is in the combine harvester's clean grain tank? How fast is the tank filling up? What is the weight of grain unloaded each time to the grain cart? How much (i.e. volume and/or weight) material is in the spreader truck? How fast is it being used up?
Measuring and keeping track of dry material quantities and rates provides important inputs to agricultural yield management systems that create maps of farm field productivity. Measuring the yield of a farm field is simple in theory, but difficult in practice. Combine harvesters, for example, are typically equipped with impact sensor plates at the top of their clean grain elevators to measure mass flow of grain before it falls toward the base of a bin loading auger. (Other types of mass flow sensors for grain include radiation, photoelectric and paddle wheel sensors.) The moisture content of the grain is estimated by passing it between capacitive sensing plates. Estimates of the amount of grain collected, as determined by integrating mass flow rates, are calibrated by comparison to grain weight measured by load cells in a grain cart. Machine movement, operating on slopes, friction effects from grain of different moisture content, and other problems can all lead to mass flow rate errors. Furthermore the inherent time lag of conventional calibration procedures reduces achievable precision and efficiency.
Thus what are needed are systems and methods to improve farmers' ability to measure quantities of dry agricultural materials and rates of change of those quantities. Also needed are systems and methods to rapidly and effectively communicate materials quantities and rates between farm equipment operators. When measurements of dry agricultural materials are accurate, rapidly available and communicated quickly to the farm workers that need them, farm yield management is improved and more crops can be produced at lower cost.